Performance prediction of a jumbo drill in ankara-pozanti motorway tunnel (Turkey)

Abstract

In this study, the performance prediction of a jumbo drill used in Pozanti-Ankara Motorway Tunnel (Kirkgecit-1) was investigated. The performance of the drill was observed in once every 50 meters of the tunnel route. Rock blocks were collected from each observation points for the laboratory tests. In addition, joint count was performed on the tunnel face in each observation point. Schmidt hammer, P-wave velocity, impact strength and density values of the rock samples were determined in the laboratory. For each observation point, volumetric joint count (JV), which is defined as the sum of the number of joints per meter for each joint set, was calculated from joint measurements. Penetration rates of the drill were firstly correlated with rock properties. It was found that there was no correlation between the penetration rate and intact rock properties. This is due to the fact that rock properties belonging to each observation point are approximately same. Then, penetration rates were correlated with Jv values and found strong correlation. Penetration rate linearly decreases with increasing Jv values. Concluding remark is that, if the intact rock properties are approximately same, drilling performance of jumbo drill depends largely on the discontinuities on the rock mass.